Magnesium compound, olefin polymerization catalyst, and method for producing olefin polymer

ABSTRACT

The invention relates to a magnesium compound effective in producing olefin polymers having an increased bulk density and a narrowed particle size distribution, not lowering the stereospecificity of the polymers produced and not lowering the polymerization activity in producing the polymers, to an olefin polymerization catalyst comprising the compound, and to a method for producing such olefin polymers. The olefin polymerization catalyst comprises (A) a solid catalyst component prepared by contacting a magnesium compound having a specific particle size distribution index (P), a titanium compound and an electron donor compound with each other, (B) an organometallic compound, and (C) an electron donor. The olefin polymerization method comprises polymerizing an olefin in the presence of the catalyst to give olefin polymers.

TECHNICAL FIELD

The present invention relates to a magnesium compound suitable for acarrier for olefin polymerization catalysts, to an olefin polymerizationcatalyst comprising it, and to a method for producing olefin polymers.Precisely, the invention relates to a magnesium compound effective inproducing olefin polymers having an increased bulk density and anarrowed particle size distribution, not lowering the stereospecificityof the polymers produced and not lowering the polymerization activity inproducing the polymers, and also relates to an olefin polymerizationcatalyst comprising the compound, and to a method for producing sucholefin polymers.

BACKGROUND ART

Heretofore widely known in the art is a technique of using a carrier ofnon-ground magnesium chloride or magnesium alkoxide for olefinpolymerization catalysts in homopolymerizing or copolymerizing ethyleneor propylene, and this is for improving the catalyst activity and forimproving the powder morphology of polymers produced. For example, knownare a method of holding a magnesium compound on an inorganic oxide suchas silica, for improving the morphology including the particle size andthe particle shape of the polymers produced in the presence of it (e.g.,Japanese Patent Laid-Open No. 280707/1988); and a method of oncedissolving a magnesium compound in a solvent of alcohol or the likefollowed by re-precipitating it, and using it in producing olefinpolymers (e.g., Japanese Patent Laid-Open No. 811/1981). However, themethods are problematic in that their steps are extremely complicatedsince they indispensably require the step of holding a magnesiumcompound on a carrier or the step of dissolving a magnesium compoundfollowed by re-precipitating it, and that the properties of thecatalysts produced are not stable. On the other hand, another method hasbeen developed, which comprises reacting metal magnesium with alcoholand a specific amount of halogen to prepare a magnesium compound forcarrier (e.g., Japanese Patent Laid-Open No. 130107/1992). However, thisis still problematic in that the powder morphology (a bulk density, aparticle size distribution or the like) of the polymers produced in thepresence of it is not all the time satisfactory.

The present invention has been made in consideration of the mattersnoted above, and its object is to provide a magnesium compound effectivein producing olefin polymers having an increased bulk density and anarrowed particle size distribution, not lowering the stereospecificityof the polymers produced and not lowering the polymerization activity inproducing the polymers, and also to provide an olefin polymerizationcatalyst comprising the compound and a method for producing such olefinpolymers.

DISCLOSURE OF THE INVENTION

We, the present inventors have assiduously studied in order to attainthe object as above, and have found that the object can be attained byan olefin polymerization catalyst that comprises a solid catalystcomponent prepared by contacting a magnesium compound (this is preparedby reacting a metal magnesium, an alcohol, and at least 0.0001 gramatoms, in terms of the halogen atom relative to one gram atom ofmagnesium, of a halogen and/or a halogen-containing compound, at aspecifically controlled temperature) with titanium and optionally withan electron donor compound, and an organoaluminium compound. On thebasis of this finding, we have completed the first aspect of theinvention.

Specifically, the first aspect of the invention is to provide amagnesium compound, an olefin polymerization catalyst and a method forproducing olefin polymers mentioned below.

1. A magnesium compound obtained by reacting a metal magnesium, analcohol, and at least 0.0001 gram atoms, in terms magnesium, an alcohol,and at least 0.0001 gram atoms, in terms of the halogen atom relative toone gram atom of magnesium, of a halogen and/or a halogen-containingcompound, at 30 to 60° C.

2. The magnesium compound of above 1, wherein the halogen is iodine.

3. The magnesium compound of above 1, wherein the halogen-containingcompound is magnesium chloride.

4. A solid magnesium compound substantially comprising a magnesiumalkoxide, of which the particle size distribution index (P) representedby the following formula (I-1) is smaller than 4.0, P<4.0:

P=(D ₉₀ /D ₁₀)  (I-1)

(wherein D₉₀ indicates the particle diameter of the compound particlescorresponding to the cumulative weight fraction of 90% in the particlesize distribution thereof computed from the light transmittance througha suspension of the compound particles in a hydrocarbon; and D₁₀indicates the particle diameter of the compound particles correspondingto the cumulative weight fraction of 10% therein.)

5. An olefin polymerization catalyst comprising (A) a solid catalystcomponent prepared by contacting (a) the magnesium compound of any ofabove 1 to 4 with (b) a titanium compound of the following generalformula (I-3), and (B) an organometallic compound:

 Ti(OR)_(n)X_(4−n)  (I-3)

(wherein X indicates a halogen atom; R indicates a hydrocarbon grouphaving from 1 to 10 carbon atoms, and R's may be the same or different;and n indicates an integer of from 0 to 4.)

6. An olefin polymerization catalyst comprising (A) a solid catalystcomponent prepared by contacting (a) the magnesium compound of any ofabove 1 to 4, (b) a titanium compound of the following general formula(I-3) and (c) an electron donor compound with each other, (B) anorganometallic compound, and (C) a third component of an electron donorcompound:

Ti(OR)_(n)X_(4−n)  (I-3)

(wherein X indicates a halogen atom; R indicates a hydrocarbon grouphaving from 1 to 10 carbon atoms, and R's may be the same or different;and n indicates an integer of from 0 to 4.)

7. A method for producing olefin polymers, which comprises polymerizingan olefin in the presence of the olefin polymerization catalyst of above5 or 6.

We, the present inventors have further found that the object of theinvention can be attained by an olefin polymerization catalyst thatcomprises a solid catalyst component prepared by contacting a specificmagnesium compound (this is prepared by reacting a metal magnesium, analcohol, and at least 0.0005 gram atoms, in terms of the halogen atomrelative to one gram atom of magnesium, of a halogen and/or hydrocarboncompound) with titanium and optionally with an electron donor compound,and an organoaluminium compound. On the basis of this finding, we havecompleted the second aspect of the invention.

Specifically, the second aspect of the invention is to provide amagnesium compound, an olefin polymerization catalyst and a method forproducing olefin polymers mentioned below.

1. A magnesium compound obtained by reacting a metal magnesium, analcohol, and at least 0.0005 gram atoms, in terms of the halogen atomrelative to one gram atom of magnesium, of a halogen and/or ahalogen-containing compound, in the presence of a saturated hydrocarboncompound.

2. The magnesium compound of above 1, wherein the halogen is iodine.

3. The magnesium compound of above 1, wherein the halogen-containingcompound is magnesium chloride.

4. A solid magnesium compound substantially comprising a magnesiumalkoxide, of which the particle size distribution index (P) representedby the following formula (II-1) is smaller than 4.0, P<4.0:

P=(D ₉₀ /D ₁₀)  (II-1)

(wherein D₉₀ indicates the particle diameter of the compound particlescorresponding to the cumulative weight fraction of 90% in the particlesize distribution thereof computed from 90% in the particle sizedistribution thereof computed from the light transmittance through asuspension of the compound particles in a hydrocarbon; and D₁₀ indicatesthe particle diameter of the compound particles corresponding to thecumulative weight fraction of 10% therein.)

5. An olefin polymerization catalyst comprising (A) a solid catalystcomponent prepared by contacting (a) the magnesium compound of any ofabove 1 to 4 with (b) a titanium compound of the following generalformula (II-3), and (B) an organometallic compound:

Ti(OR)_(n)X_(4−n)  (II-3)

(wherein X indicates a halogen atom; R indicates a hydrocarbon grouphaving from 1 to 10 carbon atoms, and R's may be the same or different;and n indicates an integer of from 0 to 4.

6. An olefin polymerization catalyst comprising (A) a solid catalystcomponent prepared by contacting (a) the magnesium compound of any ofabove 1 to 4, (b) a titanium compound of the following general formula(II-3) and (c) an electron donor compound with each other, (B) anorganometallic compound, and (C) a third component of an electron donorcompound:

Ti(OR)_(n)X_(4−n)  (II-3)

(wherein X indicates a halogen atom; R indicates a hydrocarbon grouphaving from 1 to 10 carbon atoms, and R's may be the same or different;and n indicates an integer of from 0 to 4.) comprises polymerizing anolefin in the presence of the olefin polymerization catalyst of above 5or 6.

BEST MODES OF CARRYING OUT THE INVENTION

Modes of carrying out the invention are described below.

[I] First Aspect of the Invention

The first aspect of the invention (in this section, this will be simplyreferred to as “the invention”) is to provide the magnesium compound,the olefin polymerization catalyst and the method for producing olefinpolymers as above. These are described in detail hereinunder.

[I] Magnesium Compound

The magnesium compound of the invention (this will be referred to as acarrier) is obtained by reacting a metal magnesium, an alcohol, and atleast 0.0001 gram atoms, in terms of the halogen atom relative to onegram atom of magnesium, of a halogen and/or a halogen-containingcompound, at 30 to 60° C. For this, the morphology of the metalmagnesium is not specifically defined. Therefore, metal magnesium of anysize is employable herein, including, for example, granular, ribbon-likeand powdery metal magnesium. The surface condition of the metalmagnesium is not specifically defined, but metal magnesium not coatedwith a film of magnesium hydroxide is preferred for use herein. The typeof the alcohol for use herein is not also specifically defined, butpreferred are lower alcohols having from 1 to 6 carbon atoms. Morepreferred is ethanol, as giving a solid product with much improvedcatalytic capabilities. The purity and the water content of the alcoholare not also specifically defined. However, alcohol having a high watercontent will form magnesium hydroxide on the surface of the metalmagnesium. Therefore, the alcohol for use herein preferably has a watercontent of at most 1% by weight, more preferably at most 2000 ppm. Forbetter morphology of the magnesium compound to be obtained, the watercontent of the alcohol is preferably smaller. In general, it isdesirable that the water content of the alcohol is at most 200 ppm.

The type of the halogen is not specifically defined, but preferred ischlorine, bromine or iodine. More preferred is iodine. The type of thehalogen-containing compound is not also specifically defined, and anyand every type of compounds containing halogen atom(s) in the chemicalformula are usable herein. In the compounds, the type of the halogenatom is not specifically defined, but preferred is chlorine, bromine oriodine. Especially preferred are halogen-containing metal compounds.Preferred examples of the halogen-containing compound are MgCl₂, MgI₂,Mg(OEt)Cl, Mg(OEt)I, MgBr₂, CaCl₂, NaCl, KBr. Of those, especiallypreferred is MgCl₂. For their condition, form and granularity, thehalogen and the halogen-containing metal compound are not specificallydefined, and they may be any desired ones. For example, their solutionsin an alcohol solvent (e.g., ethanol) are acceptable herein.

The amount of the alcohol is not specifically defined, but is preferablyfrom 2 to 100 mols, more preferably from 5 to 50 mols relative to onemol of the metal magnesium. Too much alcohol, if used, will lower theyield of the magnesium compound of good morphology. However, if theamount of the alcohol used is too small, smoothly stirring the reactantsin a reactor will be impossible. However, the molar ratio defined aboveis not limitative.

The amount of the halogen and/or the halogen-containing compound to beused is at least 0.0001 gram atoms, preferably at least 0.0005 gramatoms, more preferably at least 0.001 gram atoms in terms of the halogenatom relative to one gram atom of the metal magnesium. In case where theamount of the halogen and/or the halogen-containing compound used issmaller than 0.0001 gram atoms, it does not differ from the case where ahalogen is used as a reaction initiator; and if the resulting magnesiumcompound is used as a carrier for the catalyst in olefin polymerization,the catalyst activity is poor and the polymers produced could not havegood morphology. The uppermost limit of the amount of the halogen to beused is not specifically defined, and may be suitably determined withina range within which the intended magnesium compound of the inventioncan be obtained. In general, the amount of the halogen shall be smallerthan 0.06 gram atoms. In the invention, one type or two or moredifferent types of halogen and halogen-containing compounds may be usedeither singly or as combined. If desired, a halogen and ahalogen-containing compound may be combined for use herein. Regardingthe amount of the two, if combined for use herein, the total halogencontent of the combination shall be at least 0.0001 gram atoms,preferably at least 0.0005 gram atoms, more preferably at least 0.001gram atoms, relative to one gram atom of the metal magnesium. In thiscase, the uppermost limit of the total halogen content is notspecifically defined, and may be suitably determined within a rangewithin which the intended magnesium compound of the invention can beobtained. In general, it is preferably smaller than 0.06 gram atoms. Theparticle size of the magnesium compound to be produced herein can bewell controlled by changing and controlling the amount of the halogenand/or the halogen-containing compound to be used. The reaction itselfof the metal magnesium, the alcohol, and the halogen and/or thehalogen-containing compound may be effected in any known manner, exceptthat the reaction temperature is defined to fall between 30 and 60° C.Specifically, they are reacted until hydrogen gas is no more generated,generally for 10 to 30 hours to obtain the intended magnesium compound.Concretely, in case where iodine is used as the halogen, solid iodine isput into an alcohol with a metal magnesium therein, and then reactedwith them under heat; or an alcohol solution of iodine is dropwise putinto an alcohol with a metal magnesium therein, and then heated; or analcohol solution of iodine is dropwise put into an alcohol solution of ametal magnesium under heat. Preferably, these methods are effected in aninert gas (e.g., nitrogen gas, argon gas) atmosphere. For the mode ofputting the metal magnesium, the alcohol and the halogen into thereactor, it is not always necessary that they are put thereinto all at atime in the initial stage of reaction, but they may be divided into someportions and may be intermittently put into the reactor. In onepreferred mode of reacting them, the entire amount of alcohol is firstput into a reactor before the start of the reaction, and thereaftermetal magnesium having been divided into some portions is intermittentlyput into the reactor. In this mode of reaction, it is possible to evadethe sudden generation of a large amount of hydrogen gas. Therefore, thismode of reaction is preferred, as being safe. The other advantages ofthis mode of reaction are that the reactor to be used may be down-sized,and that the alcohol and the halogen put into the reactor are preventedfrom being scattered in and around the reactor since the reaction doesnot give a large amount of hydrogen gas. The number of the dividedportions of the metal magnesium and the frequency of adding thethus-divided metal magnesium portions to the reactor shall bedetermined, depending on the scale of the reactor used, and is notspecifically defined. In view of the easiness in completing thereaction, the frequency of adding the divided metal magnesium portionsto the reactor will be generally from 5 to 10 times. Needless-to-say,the reaction may be effected in any mode of batch reaction or continuousreaction. In another modification of the reaction, a small amount ofmetal magnesium is put into a reactor already containing the entireamount of alcohol, then the reaction product produced is separated andtaken out into a different tank, and thereafter a small amount of metalmagnesium is again put into the reactor, and this process is repeated.

In the invention, the reaction must be effected at 30 to 60° C. Withinthe limited temperature range, it is easy to obtain a magnesium compoundcapable of giving an olefin polymer having a higher bulk density and amore narrowed particle size distribution than conventionally.

In case where the magnesium compound obtained in the manner as above isused in producing the solid catalyst component (A) (this will bementioned hereinunder), it may be dried or may be washed with an inertsolvent such as heptane, after having been filtered out of the reactionmixture and before being used in producing the solid catalyst component(A). Anyhow, the magnesium compound obtained can be directly used in thenext step, without being further ground or classified to dress itsparticles. The particles of the magnesium compound of the invention thusobtained are more spherical and have a more narrowed and sharperparticle size distribution than those of any other conventionalmagnesium compounds. In addition, the distribution of sphericity of theindividual particles is narrow.

The invention also provides a solid magnesium compound substantiallycomprising a magnesium alkoxide, of which the particle size distributionindex (P) represented by the following formula (I-1) is smaller than4.0, P<4.0.

P=(D ₉₀ /D ₁₀)  (I-1)

(wherein D₉₀ indicates the particle diameter of the compound particlescorresponding to the cumulative weight fraction of 90% in the particlesize distribution thereof computed from the light transmittance througha suspension of the compound particles in a hydrocarbon; and D₁₀indicates the particle diameter of the compound particles correspondingto the cumulative weight fraction of 10% therein.)

P is the particle size distribution index of a particulate compound,indicating the degree of the particle size distribution of the compound.A particulate compound having a smaller value of P has a narrower andsharper particle size distribution, and therefore contains a largeramount of particles having a uniform particle size. To that effect, thesolid magnesium compound of the invention preferably has P of smallerthan 3.8, P<3.8.

Also preferably, the solid magnesium compound has a degree of sphericity(S) of the following formula (I-2) of smaller than 2.0, S<2.0.

S=(L ₁ /L ₂)³  (I-2)

(wherein L₁ indicates the major diameter of the magnesium compoundparticle obtained by imaging the compound through scanning electronicmicroscopy followed by analyzing the projected image of the particle;and L₂ indicates the diameter of the circle having the same area as theprojected area of the magnesium compound particle.)

S indicates the degree of sphericity of a substance, and a substancehaving S=1 is a complete sphere. Therefore, the magnesium compound ofwhich S is nearer to 1 means that its individual particles are nearer tocomplete spheres. More preferably, the solid magnesium compound of theinvention has S of smaller than 1.5, S<1.5.

The solid magnesium compound generally has a mean particle size of from10 to 100 μm. When compared with conventional magnesium compounds ofwhich the mean particle size is nearly the same as that of the solidmagnesium compound of the invention, the solid magnesium compound of theinvention has a smaller degree of sphericity, S, than that of theconventional magnesium compounds, and therefore its particlesconventional magnesium compounds, and therefore its particles are nearerto complete spheres than the conventional magnesium compound particles.The solid magnesium compound of this type of the invention may beproduced according to the method mentioned hereinabove.

[II] Olefin Polymerization Catalyst

The olefin polymerization catalyst of the invention comprises (A) asolid catalyst component prepared by contacting (a) the magnesiumcompound mentioned above, (b) a titanium compound of the followinggeneral formula (I-3) and optionally (c) an electron donor compound witheach other, (B) an organometallic compound, and optionally (C) a thirdcomponent of an electron donor compound.

Ti(OR)_(n)X_(4−n)  (I-3)

(wherein X indicates a halogen atom; R indicates a hydrocarbon grouphaving from 1 to 10 carbon atoms, and R's may be the same or different;and n indicates an integer of from 0 to 4.)

The constituent components are described below.

Component (A)

The component (A) is a solid catalyst component prepared by contacting(a) the magnesium compound mentioned above, (b) a titanium compound offormula (I-3) and optionally (c) an electron donor compound with eachother.

Component (a)

The component (a) is the magnesium compound mentioned

Component (b)

The component (b) is a titanium compound of formula (I-3). In formula(I-3), X indicates a halogen atom, and is preferably a chlorine atom ora bromine atom, more preferably a chlorine atom. R indicates ahydrocarbon group, and it may be saturated or unsaturated, and may belinear, branched or cyclic. It may contain hetero atoms of sulfur,nitrogen, oxygen, silicon, phosphorus and others. Preferably, R is ahydrocarbon group having from 1 to 10 carbon atoms, more preferably analkyl group, an alkenyl group, a cycloalkenyl group, an aryl group or anaralkyl group, even more preferably a linear or branched alkyl group. Aplurality —OR groups, if any, in the formula may be the same ordifferent. Specific examples of R include a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, asec-butyl group, an isobutyl group, an n-pentyl group, an n-hexyl group,an n-heptyl group, an n-octyl group, an n-decyl group, an allyl group, abutenyl group, a cyclopentyl group, a cyclohexyl group, a cyclohexenylgroup, a phenyl group, a tolyl group, a benzyl group, a phenethyl group,etc. n indicates an integer of from 0 to 4.

Specific examples of the titanium compound of formula (I-3) includetetraalkoxytitaniums such as tetramethoxytitanium, tetraethoxytitanium,tetra-n-propoxytitanium, tetraisopropoxytitanium,tetra-n-butoxytitanium, tetraisobutoxytitanium,tetracyclohexyloxytitanium, tetraphenoxytitanium, etc.; titaniumtetrahalides such as titanium tetrachloride, titanium tetrabromide,titanium tetraiodide, etc.; alkoxytitaniumtrihalides such asmethoxytitaniumtrichloride, ethoxytitanium trichloride,n-propoxytitanium trichloride, n-butoxytitanium trichloride,ethoxytitanium tribromide, etc.; dialkoxytitanium dihalides such asdimethoxytitanium dichloride, diethoxytitanium dichloride,diisopropoxytitanium dichloride, di-n-propoxytitanium dichloride,diethoxytitanium dibromide, etc.; trialkoxytitanium monohalides such astrimethoxytitanium chloride, triethoxytitanium chloride,triisopropoxytitanium chloride, tri-n-propoxytitanium chloride,tri-n-butoxytitanium chloride, etc. Of those, preferred are high-halogentitanium compounds, and especially preferred is titanium tetrachloride.One or more of these titanium compounds may be used herein either singlyor as combined.

Electron Donor Compound (c)

In the invention, optionally used is an electron donor compound (c). Theelectron donor compound (c) improves the stereospecificity of the olefinpolymers produced, and using it in the invention is preferred. Theelectron donor compound (c) includes oxygen-containing electron donors,for example, alcohols, phenols, ketones, aldehydes, carboxylic acids,malonic acid, esters of organic acids or inorganic acids, ethers such asmonoethers, diethers or polyethers, etc.; and nitrogen-containingelectron donors such as ammonia, amines, nitriles, isocyanates, etc. Ofthose, preferred are ester of polycarboxylates, and more preferred areesters of aromatic polycarboxylates. Even more preferred are esters ofaromatic dicarboxylates. Preferably, the organic group in the estermoiety of these esters is a linear, branched or cyclic aliphatichydrocarbon residue.

Concretely mentioned are dialkyl esters of dicarboxylic acids such asphthalic acid, naphthalene-1,2-dicarboxylic acid,naphthalene-2,3-dicarboxylic acid,5,6,7,8-tetrahydronaphthalene-1,2-dicarboxylic acid,5,6,7,8-tetrahydronaphthalene-2,3-dicarboxylic acid,indane-4,5-dicarboxylic acid, indane-5,6-dicarboxylic acid, etc., inwhich the alkyl groups may be any of methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, t-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl,3-methylbutyl, 1,1-dimethylpropyl, 1-methylpentyl, 2-methylpentyl,3-methylpentyl, 4-methylpentyl, 1-ethylbutyl, 2-ethyl, n-hexyl,cyclohexyl, n-heptyl, n-octyl, n-nonyl, 2-methylhexyl, 3-methylhexyl,4-methylhexyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl, 2-ethylpentyl,and 3-ethylpentyl groups. Of these, preferred are diphthalates.Preferably, the organic group in the ester moiety of these esters is alinear or branched aliphatic hydrocarbon residue having at least 4carbon atoms.

The solid catalyst component (A) is prepared by contacting the magnesiumcompound (a), the titanium compound (b) and optionally the electrondonor compound (c) and further optionally a halide (d) such as silicontetrachloride with each other, and they be contacted and reacted witheach other in any ordinary manner. Some preferred conditions for theiramount and the order in which they are contacted with each other arementioned below.

The amount of the titanium compound (b) to be used may fall generallybetween 0.5 and 100 mols, but preferably between 1 and 50 mols, per molof magnesium of the magnesium compound (a). The amount of the electrondonor compound (c) to be used may fall generally between 0.01 and 10mols, but preferably between 0.05 and 0.15 mols, per mol of magnesium ofthe magnesium compound (a). For the halide (d), preferred are silicontetrachloride, silicon tetrabromide, tin tetrachloride, tin tetrabromideand hydrogen chloride; and more preferred is silicon tetrachloride. Thetemperature at which the constituent components are contacted with eachother to prepare the solid catalyst component may fall generally between−20 and 200° C., but preferably between 20 and 150° C.; and the contacttime for them may fall generally between 1 minute and 24 hours, butpreferably between 10 minutes and 6 hours. The order of contacting themwith each other is not specifically defined. For example, theconstituent components may be contacted with each other in an inertsolvent such as hydrocarbons, etc.; or, as the case may be, they areseparately diluted with an inert solvent such as hydrocarbons, etc., andthen contacted with each other. The inert solvent includes, for example,aliphatic hydrocarbons such as n-pentane, isopentane, n-hexane,n-heptane, n-octane, isooctane, etc.; aromatic hydrocarbons such asbenzene, toluene, xylene, etc.; and their mixtures.

Preferably, the titanium compound is contacted twice or more with themagnesium compound serving as a carrier, so that it can be well held onthe magnesium compound.

The solid catalyst component thus prepared through the contact treatmentas above may be washed with an inert solvent such as hydrocarbons, etc.For the inert solvent, usable are those mentioned above. The solidcatalyst component may be stored in dry, or may be stored in an inertsolvent such as hydrocarbons, etc.

Component (B)

The component (B) includes organoaluminium compounds. Theorganoaluminium compounds for it are not specifically defined, butpreferred are those having any of alkyl groups, halogen atoms, hydrogenatoms and alkoxy groups, aluminoxanes, and their mixtures. Concretely,they include trialkylaluminiums such as trimethylaluminium,triethylaluminium, triisopropylaluminium, triisobutylaluminium,trioctylaluminium, etc.; dialkylaluminium monochlorides such asdiethylaluminium monochloride, diisopropylaluminium monochloride,diisobutylaluminium monochloride, dioctylaluminium monochloride, etc.;alkylaluminium sesquihalides such as ethylaluminium sesquichloride,etc.; linear aluminoxanes such as methylaluminoxane, etc. Of thoseorganoaluminium compounds, preferred are trialkylaluminiums with loweralkyl groups each having from 1 to 5 carbon atoms; and more preferredare trimethylaluminium, triethylaluminium, triisopropylaluminium, andtriisobutylaluminium. One or more of these organoaluminium compounds areusable herein either singly or as combined.

Electron Donor Compound (C)

In the invention, optionally used is a third component of an electrondonor compound (C). Using an electron donor compound is preferred, asimproving the stereospecificity of the olefin polymers produced. Thecomponent (C) includes alkoxy group-having organosilicon compounds,nitrogen-containing compounds, phosphorus-containing compounds, andoxygen-containing compounds. Of those, especially preferred are alkoxygroup-having organosilicon compounds. Specific examples of the compoundsare trimethylmethoxysilane, triethylmethoxysilane,dimethyldimethoxysilane, dimethyldiethoxysilane,diphenyldimethoxysilane, dimethyldiethoxysilane,diphenyldimethoxysilane, diphenyldiethoxysilane,dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane,cyclohexyl-iso-butyldimethoxysilane,cyclohexyl-1,1,2-trimethylpropyldimethoxysilane,α-naphthyl-1,1,2-trimethylpropyldimethoxysilane,n-tetradecanyl-1,1,2-trimethylpropyldimethoxysilane,cyclopentylmethyldimethoxysilane, cyclopentylethyldimethoxysilane,cyclopentylpropyldimethoxysilane, cyclopentyl-t-butyldimethoxysilane,cyclopentyl-1,1,2-trimethylpropyldimethoxysilane,dicyclopentyldimethoxysilane, cyclopentylcyclohexyldimethoxysilane,t-butylmethyldimethoxysilane, t-butylethyldimethoxysilane,t-butylpropyldimethoxysilane, di-t-butyldimethoxysilane,diisopropyldimethoxysilane, isopropylisobutyldimethoxysilane,γ-chloropropyltrimethoxysilane, methyltriethoxysilane,ethyltriethoxysilane, vinyltriethoxysilane, butyltriethoxysilane,phenyltriethoxysilane, γ-aminopropyltriethoxysilane,chlorotriethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane,methyl-t-butoxydimethoxysilane, isopropyl-t-butoxydimethoxysilane,cyclopentyl-t-butoxydimethoxysilane,1,1,2-trimethylpropyltrimethoxysilane, ethyl silicate, butyl silicate,trimethylphenoxysilane, methyltrialloxysilane, vinyltris(β-methoxyethoxy) silane, vinyltrisacetoxysilane,dimethyltetraethoxydisiloxane, etc. One or more of these organosiliconcompounds may be used herein either singly or as combined.

The amount of the catalyst components to be used is not specificallydefined. In general, the amount of the solid catalyst component (A) tobe used may fall between 0.0005 and 1 mmol, in terms of the titaniumatom therein, per dm³ of the reaction capacity. For the amount of theorganometallic compound (B) to be used, the atomic ratio,aluminium/titanium may fall generally between 1 and 10000, butpreferably between 10 and 1000. If the atomic ratio oversteps thedefined range, the catalyst activity will be low. For the amount of theelectron donor compound (C) to be used, the molar ratio, electron donorcompound/organoaluminium compound may fall generally between 0.02 and2.0, but preferably between 0.05 and 1.0. If the molar ratio overstepsthe defined range, the catalyst activity will also be low.

[III] Method for Producing Olefin Polymers

For producing olefin polymers according to the invention, an olefin ispolymerized in the presence of the above-mentioned olefin polymerizationcatalyst. The olefin to be polymerized herein is not specificallydefined, but preferred are α-olefins of the following general formula(I-4):

R¹—CH═CH₂  (I-4).

In formula (I-4), R¹ indicates a hydrogen atom or a hydrocarbon group,and the hydrocarbon group may be saturated or unsaturated, and may belinear, branched or cyclic. Concretely, the α-olefins include ethylene,propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene,3-methyl-1-pentene, 4-methyl-1-pentene, vinylcyclohexane, etc. One ormore of these olefins may be used herein either singly or as combined.Of the olefins mentioned above, especially preferred is propylene. Forits polymerization mode, the olefin may be homopolymerized orcopolymerized. Especially preferred is homopolymerization of propylene,or copolymerization of propylene with ethylene and/or an α-olefin havingfrom 4 to 20 carbon atoms (1-butene, 1-hexene, etc.). If desired, dienessuch as butadiene, and any other olefins may be additionally used inproducing the olefin polymers.

In the olefin polymerization method of the invention, if desired, anolefin may be first prepolymerized and then finally polymerized.Regarding its prepolymerization, for example, an olefin such as thatmentioned above is prepolymerized in the presence of the catalystmentioned above, generally at a temperature falling between 0 and 100°C. and under a pressure falling between normal pressure and 5 MPa or so.The prepolymerization time may fall between 1 minute and 10 hours,preferably between 10 minutes and 5 hours. The degree ofprepolymerization may fall generally between 0.1 and 1000% by weight,but preferably between 1 and 500% by weight, relative to the solidcatalyst component used. The olefin to be prepolymerized may be any ofthe above-mentioned α-olefins. Preferably, however, it is the sameα-olefin as that to be finally polymerized to give the intended olefinpolymer. Next, in the presence of the catalyst and thethus-prepolymerized product, an olefin is finally polymerized to givethe intended olefin polymer. The mode of final polymerization is notspecifically defined, and may be any of solution polymerization, slurrypolymerization, vapor-phase polymerization or bulk polymerization. Anyof batch polymerization and continuous polymerization may apply thereto.If desired, two-stage polymerization in which the two stages areeffected under different conditions, or block polymerization in which anadditional α-olefin such as ethylene, 1-butene or 1-hexene isblock-polymerized in the second stage may also apply to the invention.Further, multi-stage polymerization may apply thereto. Regarding thereaction condition for the method of the invention, the polymerizationpressure is not specifically defined and may fall generally betweenatmospheric pressure and 8 MPa, but preferably between 0.2 and 5 MPa;the polymerization temperature may fall generally between 20 and 90° C.,but preferably between 40 and 90° C. The polymerization time shall vary,depending on the type of the starting olefin and on the polymerizationtemperature, and could not be indiscriminately defined. In general,however, it may fall between 5 minutes and 20 hours, preferably between10 minutes and 10 hours or so. The molecular weight of the polymer to beproduced can be controlled by adding a chain transfer agent to thepolymerization system, preferably hydrogen thereto. If desired, an inertgas such as nitrogen or the like may be present in the polymerizationsystem.

Regarding the catalyst components for use in the invention, thecomponent (A), the component (B) and the component (C) may be previouslyblended in a pre-determined ratio so that they are contacted with eachother, and immediately an olefin may be applied thereto to start itspolymerization. Alternatively, after the catalyst components have beencontacted with each other, the resulting catalyst may be ripened for 0.2to 3 hours or so, and thereafter an olefin may be applied thereto andpolymerized in the presence of the thus-ripened catalyst. If desired,the catalyst components may be previously suspended in an inert solventor olefin, and then fed into the polymerization system.

In the invention, the post-treatment after polymerization may beeffected in any ordinary manner. For example, in vapor-phasepolymerization, the powdery polymer produced is taken out of thepolymerization reactor, and then exposed to a nitrogen stream atmosphereso as to remove the non-reacted olefin from it. If desired, the polymermay be pelletized through an extruder. In this step, a small amount ofwater, an alcohol or the like may be added to the polymer so as tocompletely inactivate the catalyst. In bulk polymerization, the polymerproduced is taken out of the polymerization reactor, then thenon-reacted monomer is completely removed from it, and thereafter thepolymer may be pelletized. According to the method of the invention, thepowdery olefin polymer produced has the advantages of high bulk densityand narrow particle size distribution. Other advantages of the inventionare that the polymer produced has good stereospecificity and that thecatalyst used has high polymerization activity. For example, inhomopolymerization of propylene in the method, produced is a propylenehomopolymer having a bulk density (kg/m³) of at least 340, preferably atleast 380, and having good stereospecificity, and the catalyst usedexhibits high polymerization activity. In addition, the propylenehomopolymer thus produced has a particle size distribution index (P′) ofsmaller than 4.0, P′<4.0, preferably smaller than 3.8, P′<3.8. That is,the particle size distribution of the propylene homopolymer is narrowerthan that of conventional propylene homopolymers. The method forcomputing the particle size distribution index of the polymer isdescribed in detail in the next section of Examples. When compared withconventional propylene homopolymers of which the mean particle size isnearly the same as that of the propylene homopolymer produced accordingto the method of the invention, the propylene homopolymer produced inthe invention has a smaller degree of sphericity (S′) than that of theconventional propylene homopolymers. For its powdery morphology, theparticles of the propylene homopolymer produced in the invention arenearer to complete spheres than those of conventional propylenehomopolymers. The method for computing the degree of sphericity of thepolymer is described in detail in the next section of Examples.

The invention is described in more detail with reference to thefollowing Examples, which, however, are not intended to restrict thescope of the invention.

The methods for analyzing and evaluating the polymers of the inventionare described below.

(1) Stereospecificity [mmmm]

A sample of the polymer to be analyzed is dissolved in1,2,4-trichlorobenzene, and subjected to a proton complete decouplingmethod for ¹³C-NMR (using JEOL' EX-400) at 130° C. Based on the signalsfor the methyl group obtained in the method, the stereospecificity[mmmm] of the sample is determined. The isotactic pentad fraction [mmmm]referred to herein for polymer stereospecificity was proposed by A.Zambelli et al. in Macromolecules, 6, 925 (1973), and it indicates theisotactic fraction in the pentad units of a polypropylene molecularchain measured in ¹³C nuclear magnetic resonance spectrometry. For theattribution of the peaks seen in the ¹³C nuclear magnetic resonancespectrometry, referred to is the A. Zambelli et al's proposal inMacromolecules, 8, 687 (1975).

(2) Particle Size Distribution Index (P) of Magnesium Compound

A sample of the magnesium compound to be analyzed is suspended in ahydrocarbon, and its particle size is obtained from the lighttransmittance through the suspension. The thus-obtained particle sizedistribution is plotted on a logarithmico-normal probability paper, andthe 50% particle size read thereon is the mean particle size of thesample. The particle diameter of the sample particles corresponding tothe cumulative weight fraction of 90% in the thus-plotted particle sizedistribution thereof is represented by D₉₀; and that of the sampleparticles corresponding to the cumulative weight fraction of 10% thereinis represented by D₁₀. From these, the particle size distribution index,P, of the magnesium compound is obtained according to theabove-mentioned formula (I-1).

(3) Sphericity (S) of Magnesium Compound

A dry sample of the magnesium compound to be analyzed is photographedwith a scanning electronic microscope (JEOL's JSM-25SIII) at anaccelerated voltage of 5 KV to obtain a 300-magnification negativeimage. The negative image is analyzed according to a light transmissionmethod, for which is used an image analyzer (from Nexsus). Precisely,the particles of not larger than 20 pixels (one pixel has a size of0.695 μm×0.695 μm) are cut off on the image, and about 2000 of theremaining particles are analyzed. The major diameter of the projectedimage of the particle is represented by L₁; and the diameter of thecircle having the same area as the projected area of the particle isrepresented by L₂. From these, the sphericity, S, of the magnesiumcompound is obtained according to the above-mentioned formula (I-2).

(4) Particle Size Distribution Index (P′) of Polyolefin Powder

The particle size distribution index (P′) of polyolefin powder isobtained as follows: A sample of the polyolefin powder to be analyzed issieved and measured to determine its particle size distribution. Thethus-obtained particle size distribution is plotted on alogarithmico-normal probability paper, and the 50% particle size readthereon is the mean particle size of the sample. The particle diameterof the sample particles corresponding to the cumulative weight fractionof 90% in the thus-plotted particle size distribution thereof isrepresented by D₉₀; and that of the sample particles corresponding tothe cumulative weight fraction of 10% therein is represented by D₁₀.From these, the particle size distribution index, P′, of the polyolefinpowder is obtained, as in the above-mentioned formula (I-1).

(5) Sphericity (S′) of Polyolefin Powder

In the same manner as that for analyzing the magnesium compoundparticles as above, the sample of the polyolefin powder to be analyzedis photographed with a polarizing microscope (Olympus's BHS-751P) toobtain a 40-magnification image, and the image is analyzed. One pixelsize herein is 10.4 μm×10.4 μm; and about 300 particles are analyzed.From the data of L₁ and L₂ computed in the same manner as above, thesphericity, S′, of the polyolefin powder is obtained, as in theabove-mentioned formula (I-2).

(6) Bulk Density of Polyolefin Powder

Measured according to JIS K6721.

EXAMPLE I-1

(1) Preparation of Magnesium Compound

122 g (2.64 gram atoms) of dewatered ethanol, 0.8 g (6.3 milligramatoms) of iodine, and 8 g (0.33 gram atoms) of metal magnesium were putinto a 0.5 dm³ three-neck flask equipped with a stirrer and purged withnitrogen, and these were reacted with stirring (5.83 sec⁻¹, 350 rpm) at40° C. until hydrogen gas was no more generated. A magnesium compoundwas thus obtained.

(2) Preparation of Solid Catalyst Component

A 0.5 dm³ three-neck flask equipped with a stirrer was purged withnitrogen, and 16 g of the magnesium compound obtained in the step (1)was put thereinto, to which was added 0.080 dm³ of dewatered octane.This was heated at 40° C., and 0.0024 dm³ (23 mmols) of silicontetrachloride was added thereto and stirred for 20 minutes, to which wasadded 0.0035 dm³ (13 mmols) of di-n-butyl phthalate. The resultingsolution was further heated up to 80° C., and 0.062 dm³ (0.56 mols) oftitanium tetrachloride was dropwise added thereto through a droppingfunnel. Next, the flask was still further heated to have an innertemperature of 125° C., at which the compounds therein were contactedwith each other for 2 hours. After this, the reaction mixture was fullywashed with dewatered octane. 0.107 dm³ (0.98 mols) of titaniumtetrachloride was added to this, and heated to have an inner temperatureof 125° C., at which the compounds were again contacted with each otherfor 2 hours. Next, this was fully washed with dewatered octane. Thus wasobtained a solid catalyst component.

(3) Propylene Slurry Polymerization

A one dm³ stainless autoclave equipped with a stirrer was fully driedand purged with nitrogen, and 0.4 dm³ of dewatered heptane was put intoit. 2.0 mmols of triethylaluminium and then 0.25 mmols ofdicyclopentyldimethoxysilane (DCPDMS) were added thereto in that order.Then, 0.0025 mmols, in terms of Ti, of the solid catalyst componentprepared in (2) was added thereto, and hydrogen (0.1 MPa) and propylenewere introduced thereinto in that order to have a total pressure of 0.8MPa. With that, the monomer propylene was polymerized at 80° C. for 1hour. Next, the system was cooled and degassed, and the reaction mixturewas taken out of it. This was put into 2 dm³ of methanol, and then driedin vacuum to obtain polypropylene. The results are given in Table I-1and Table I-2.

COMPARATIVE EXAMPLE I-1

(1) Preparation of Magnesium Compound

The same process as in Example I-1 was repeated, except that thereaction temperature herein was about 78° C. (at which the reactantswere in reflux)

(2) Preparation of Solid Catalyst Component

The same process as in Example I-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example I-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table I-1 and Table-2. The particle size distribution index (P)of the carrier was over 4.0; and the bulk density of the polymerobtained was 310 (kg/m³) and was low.

EXAMPLE I-2

(1) Preparation of Magnesium Compound

The same process as in Example I-1 was repeated, except that thereaction temperature herein was 50° C.

(2) Preparation of Solid Catalyst Component

The same process as in Example I-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example I-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table I-1 and Table I-2.

EXAMPLE I-3

(1) Preparation of Magnesium Compound

The same process as in Example I-2 was repeated, except that the amountof iodine used herein was 0.24 g (1.9 milligram atoms) and that thenumber of revolution was 8.75 sec⁻¹ (525 rpm).

(2) Preparation of Solid Catalyst Component

The same process as in Example I-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example I-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table I-1 and Table I-2.

COMPARATIVE EXAMPLE I-2

(1) Preparation of Magnesium Compound

The same process as in Example I-3 was repeated, except that thereaction temperature herein was about 78° C. (at which the reactantswere in reflux).

(2) Preparation of Solid Catalyst Component

The same process as in Example I-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example I-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table I-1 and Table I-2. The particle size distribution index(P) of the carrier was over 4.0; and the bulk density of the polymerobtained was 310 (kg/m³) and was low.

EXAMPLE I-4

(1) Preparation of Magnesium Compound

The same process as in Example I-1 was repeated, except that MgCl₂ (0.3g, 6.3 milligram atoms per Cl) was used for the halide.

(2) Preparation of Solid Catalyst Component

The same process as in Example I-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example I-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table I-1 and Table I-2.

COMPARATIVE EXAMPLE I-3

(1) Preparation of Magnesium Compound

The same process as in Example I-4 was repeated, except that thereaction temperature herein was about 78° C. (at which the reactantswere in reflux).

(2) Preparation of Solid Catalyst Component

The same process as in Example I-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example I-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table I-1 and Table I-2. The particle size distribution index(P) of the carrier was over 4.0; and the bulk density of the polymerobtained was 330 (kg/m³) and was low.

EXAMPLE I-5

(1) Preparation of Magnesium Compound

The same process as in Example I-1 was repeated, except that thereaction temperature herein was 60° C.

(2) Preparation of Solid Catalyst Component

The same process as in Example I-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example I-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table I-1 and Table I-2.

EXAMPLE I-6

(1) Preparation of Magnesium Compound

The same process as in Example I-1 was repeated.

(2) Preparation of Solid Catalyst Component

The same process as in Example I-1 was repeated.

(3) Propylene Slurry Polymerization

The same process as in Example I-1 was repeated, except thatcyclohexylisobutyldimethoxysilane (CHIBDMS) and notdicyclopentyldimethoxysilane (DCPDMS) was used herein for the silanecompound. The results are given in Table I-1 and Table I-2.

TABLE I-1 Comp. Comp. Comp. Example I-1 Example I-2 Example I-3 ExampleI-4 Example I-5 Example I-6 Ex. I-1 Ex. I-2 Ex. I-3 Reaction 40 50 50 5060 40 78 78 78 Temperature (° C.) Halogen or iodine iodine iodine MgCl₂iodine iodine iodine iodine MgCl₂ Halogen Compound Halogen or 0.0190.019 0.0057 0.0057 0.019 0.019 0.019 0.0057 0.0057 Halogen Compound/Mg(ratio by gram atom) Number of 5.83 5.83 8.75 8.75 5.83 5.83 5.83 8.758.75 Revolution (sec⁻¹) Mean Particle 45 52 38 38 60 45 70 43 46 Size ofCarrier (μm) Sphericity of 1.30 1.31 1.31 1.33 1.33 1.31 1.33 1.57 1.62Carrier (S) Particle Size 3.6 3.5 3.4 3.6 3.6 3.7 4.3 4.8 4.9Distribution Index of Carrier (P)

TABLE I-2 Example Example Example Example Example Example Comp. Comp.Comp. I-1 I-2 I-3 I-4 I-5 I-6 Ex. I-1 Ex. I-2 Ex. I-3 Silane DCPDMSDCPDMS DCPDMS DCPDMS DCPDMS CHIBDMS DCPDMS DCPDMS DCPDMS CompoundStereo- 98.2 98.2 98.4 98.4 98.4 97.8 98.2 98.0 98.2 specificity (mol %)Activity (kg/g- 16 18 20 19 17 12 14 13 14 cat.) Mean Particle 1100 12001000 1000 1500 900 1800 1500 1600 Size of Polymer (μm) Sphericity of1.31 1.33 1.33 1.31 1.30 1.33 1.31 1.52 1.57 Polymer (S′) Particle Size3.6 3.5 3.5 3.6 3.6 3.6 4.2 4.6 4.8 Distribution Index of Polymer (P′)Bulk Density of 410 400 420 410 380 410 310 310 330 Polymer (kg/cm³)

[II] Second Aspect of the Invention

The SECOND aspect of the invention (in this section, this will be simplyreferred to as “the invention”) is described in detail hereinunder.

[I] Magnesium Compound

The magnesium compound of the invention (this will be referred to as acarrier) is obtained by reacting a metal magnesium, an alcohol, and atleast 0.0005 gram atoms, in terms of the halogen atom relative to onegram mol of magnesium, of a halogen and/or a halogen-containingcompound, in the presence of a saturated hydrocarbon compound.

For the details of the metal magnesium, the type, the amount, the purityand the water content of the alcohol, and the type of the halogen andthe halogen-containing compound in this case, referred to are thosementioned in the section of the magnesium compound in the first aspectof the invention.

The amount of the halogen and/or the halogen-containing compound to beused herein is at least 0.0005 gram atoms, preferably at least 0.001gram atoms, more preferably at least 0.002 gram atoms in terms of thehalogen atom relative to one gram atom of the metal magnesium. In casewhere the amount of the halogen and/or the halogen-containing compoundused is smaller than 0.0005 gram atoms, it does not differ from the casewhere a halogen is used as a reaction initiator; and if the resultingmagnesium compound is used as a carrier for the catalyst in olefinpolymerization, the catalyst activity is poor and the polymers producedcould not have good morphology.

The uppermost limit of the amount of the halogen to be used is notspecifically defined, and may be suitably determined within a rangewithin which the intended magnesium compound of the invention can beobtained. In general, the amount of the halogen shall be smaller than0.06 gram atoms. In the invention, one type or two or more differenttypes of halogen and halogen-containing compounds may be used eithersingly or as combined. If desired, a halogen and a halogen-containingcompound may be combined for use herein. Regarding the amount of thetwo, if combined for use herein, the total halogen content of thecombination shall be at least 0.0005 gram atoms, preferably at least0.001 gram atoms, more preferably at least 0.002 gram atoms, relative toone gram atom of the metal magnesium. In this case, the uppermost limitof the total halogen content is not specifically defined, and may besuitably determined within a range within which the intended magnesiumcompound of the invention can be obtained. In general, it is preferablysmaller than 0.06 gram atoms. The particle size of the magnesiumcompound to be produced herein can be well controlled by changing andcontrolling the amount of the halogen and/or the halogen-containingcompound to be used.

The reaction itself of the metal magnesium, the alcohol, and the halogenand/or the halogen-containing compound to give the magnesium compoundmay be effected in any known manner, except that they are reacted in thepresence of a saturated hydrocarbon compound. They may be reactedgenerally at 30° C. or higher, but preferably at 40° C. or higher, morepreferably at a temperature at which they are in reflux.

For the details of the mode of putting the reactants, metal magnesium,alcohol and halogen into a reactor in this section, referred to arethose mentioned in the section of the first aspect of the invention.

In the invention, the reactants must be reacted in the presence of asaturated hydrocarbon compound, but the saturated hydrocarbon compoundfor the reaction is not specifically defined. It may be a saturatedhydrocarbon compound having from 5 to 15 carbon atoms. The saturatedhydrocarbon compound having from 5 to 15 carbon atoms may be any oflinear saturated hydrocarbon compounds, branched saturated hydrocarboncompounds or alicyclic saturated hydrocarbon compounds. Of those,especially preferred are hexane, heptane, octane and decane. Regardingthe timing in which such a saturated hydrocarbon compound is added tothe reaction system, the compound may be present in the system duringthe reaction of the reactants, metal magnesium, alcohol, and halogenand/or halogen-containing compound, or may be present therein after thereaction, or may be present therein during and after the reaction.Preferably, the compound is present in the system during and after thereaction. The amount of the saturated hydrocarbon compound to be used isnot specifically defined, so far as it does not detract from the objectof the invention. Preferably, however, it falls generally between 0.02and 5.0 times (by volume), more preferably between 0.05 and 2.5 times(by volume), even more preferably between 0.1 and 1.5 times (by volume)the amount of the alcohol. If it is smaller than 0.02 times, the bulkdensity of the polymer obtained will be low. If, however, it is largerthan 5.0 times, large-size reactors will be necessary, and, in addition,the bulk density of the polymer obtained could not be increased. In thepresence of such a saturated hydrocarbon compound, it is easy to obtaina magnesium compound capable of giving an olefin polymer having a higherbulk density and a more narrowed particle size distribution thanconventionally.

In case where the magnesium compound obtained in the manner as above isused in producing the solid catalyst component (A) (this will bementioned hereinunder), it may be dried or may be washed with an inertsolvent such as heptane, after having been filtered out of the reactionmixture and before being used in producing the solid catalyst component(A). Anyhow, the magnesium compound obtained can be directly used in thenext step, without being further ground or classified to dress itsparticles. The particles of the magnesium compound of the invention thusobtained are more spherical and have a more narrowed and sharperparticle size distribution than those of any other conventionalmagnesium compounds. In addition, the distribution of sphericity of theindividual particles is narrow.

The invention also provides a solid magnesium compound substantiallycomprising a magnesium alkoxide, of which the particle size distributionindex (P) represented by the following formula (II-1) is smaller than4.0, P<4.0.

P=(D ₉₀ /D ₁₀)  (II-1)

(wherein D₉₀, D₁₀ and P have the same meanings as those in the sectionof the first aspect of the invention.)

The solid magnesium compound of the invention preferably has P ofsmaller than 3.8, P<3.8.

Also preferably, the solid magnesium compound has a degree of sphericity(S) of the following formula (II-2) of smaller than 2.0, S<2.0.

S=(L ₁ /L ₂)³  (II-2)

(wherein L₁, L₂ and S have the same meanings as those in the section ofthe first aspect of the invention.)

More preferably, the solid magnesium compound of the invention has S ofsmaller than 1.5, S<1.5.

The solid magnesium compound generally has a mean particle size of from10 to 100 μm. When compared with conventional magnesium compounds ofwhich the mean particle conventional magnesium compounds of which themean particle size is nearly the same as that of the solid magnesiumcompound of the invention, the solid magnesium compound of the inventionhas a smaller degree of sphericity, S, than that of the conventionalmagnesium compounds, and therefore its particles are nearer to completespheres than the conventional magnesium compound particles. The solidmagnesium compound of this type of the invention may be producedaccording to the method mentioned hereinabove.

[II] Olefin Polymerization Catalyst

The olefin polymerization catalyst of the invention comprises (A) asolid catalyst component prepared by contacting (a) the magnesiumcompound mentioned above, (b) a titanium compound of the followinggeneral formula (II-3) and optionally (c) an electron donor compoundwith each other, (B) an organometallic compound, and optionally (C) athird component of an electron donor compound.

Ti(OR)_(n)X_(4−n)  (II-3)

(wherein X indicates a halogen atom; R indicates a hydrocarbon grouphaving from 1 to 10 carbon atoms, and R's may be the same or different;and n indicates an integer of from 0 to 4.)

The constituent components are described below.

Component (A)

The component (A) is a solid catalyst component prepared by contacting(a) the magnesium compound mentioned above, (b) electron donor compoundwith each other.

Component (a)

The component (a) is the magnesium compound mentioned above.

Component (b)

The component (b) is a titanium compound of formula (II-3). In formula(II-3), X indicates a halogen atom, and is preferably a chlorine atom ora bromine atom, more preferably a chlorine atom. R indicates ahydrocarbon group, and it may be saturated or unsaturated, and may belinear, branched or cyclic. It may contain hetero atoms of sulfur,nitrogen, oxygen, silicon, phosphorus and others. Preferably, R is ahydrocarbon group having from 1 to 10 carbon atoms, more preferably analkyl group, an alkenyl group, a cycloalkenyl group, an aryl group or anaralkyl group, even more preferably a linear or branched alkyl group. Aplurality —OR groups, if any, in the formula may be the same ordifferent. Specific examples of R include a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, asec-butyl group, an isobutyl group, an n-pentyl group, an n-hexyl group,an n-heptyl group, an n-octyl group, an n-decyl group, an allyl group, abutenyl group, a cyclopentyl group, a cyclohexyl group, a cyclohexenylgroup, a phenyl group, a tolyl group, a benzyl group, a phenethyl group,etc. n indicates an integer of from 0 to 4.

Specific examples of the titanium compound of formula (II-3) includetetraalkoxytitaniums such as tetramethoxytitanium, tetraethoxytitanium,tetra-n-propoxytitanium, tetraisopropoxytitanium,tetra-n-butoxytitanium, tetraisobutoxytitanium,tetracyclohexyloxytitanium, tetraphenoxytitanium, etc.; titaniumtetrahalides such as titanium tetrachloride, titanium tetrabromide,titanium tetraiodide, etc.; alkoxytitanium trihalides such asmethoxytitanium trichloride, ethoxytitanium trichloride,n-propoxytitanium trichloride, n-butoxytitanium trichloride,ethoxytitanium tribromide, etc.; dialkoxytitanium dihalides such asdimethoxytitanium dichloride, diethoxytitanium dichloride,diisopropoxytitanium dichloride, di-n-propoxytitanium dichloride,diethoxytitanium dibromide, etc.; trialkoxytitanium monohalides such astrimethoxytitanium chloride, triethoxytitanium chloride,triisopropoxytitanium chloride, tri-n-propoxytitanium chloride,tri-n-butoxytitanium chloride, etc. Of those, preferred are high-halogentitanium compounds, and especially preferred is titanium tetrachloride.One or more of these titanium compounds may be used herein either singlyor as combined.

Electron Donor Compound (c)

For the details of the electron donor compound for use herein, referredto are those mentioned in the section of “Electron Donor Compound (c)”in the first aspect of the invention. For the electron donor compoundfor use herein, preferred are diphthalates. Preferably, the organicgroup in the ester moiety of the esters is a linear or branchedaliphatic hydrocarbon residue having at least 4 carbon atoms.

The solid catalyst component (A) is prepared by contacting the magnesiumcompound (a), the titanium compound (b) and optionally the electrondonor compound (c) and further optionally a halide (d) such as silicontetrachloride with each other, and they be contacted and reacted witheach other in any ordinary manner. For the details of their amount,their condition and the order in which they are contacted with eachother, referred to are those mentioned in the section of the firstaspect of the invention. The solid catalyst component may be stored indry, or may be stored in an inert solvent such as hydrocarbons, etc.

Component (B)

The component (B) includes organoaluminium compounds. Theorganoaluminium compounds for it are not specifically defined. For theirdetails, referred to are those mentioned in the section of the firstaspect of the invention.

Electron Donor Compound (C)

In the invention, optionally used is a third component of an electrondonor compound (C). Using an electron donor compound is preferred, asimproving the stereospecificity of the olefin polymers produced. For thedetails of the electron donor compound, referred to are those mentionedin the section of “Electron Donor Compound (C)” in the first aspect ofthe invention.

The amount of the catalyst components to be used herein is notspecifically defined, and for its details, referred to are thosementioned in the section of the first aspect of the invention.

[III] Method for Producing Olefin Polymers

For producing olefin polymers according to the invention, an olefin ispolymerized in the presence of the above-mentioned olefin polymerizationcatalyst. The olefin to be polymerized herein is not specificallydefined, and for its details, referred to are those mentioned in thesection of the first aspect of the invention. One or more olefins may beused herein either singly or as combined. Of the olefins mentionedabove, especially preferred is propylene. For its polymerization mode,the olefin may be homopolymerized or copolymerized. Especially preferredis homopolymerization of propylene, or copolymerization of propylenewith ethylene and/or an α-olefin having from 4 to 20 carbon atoms(1-butene, 1-hexene, etc.). If desired, dienes such as butadiene, andany other olefins may be additionally used in producing the olefinpolymers.

In the olefin polymerization method of the invention, if desired, anolefin may be first prepolymerized and then finally polymerized. For thedetails of prepolymerization, referred to are those mentioned in thesection of the first aspect of the invention.

Regarding the catalyst components for use in the invention, thecomponent (A), the component (B) and the component (C) may be previouslyblended in a pre-determined ratio so that they are contacted with eachother, and immediately an olefin may be applied thereto to start itspolymerization. Alternatively, after the catalyst components have beencontacted with each other, the resulting catalyst may be ripened for 0.2to 3 hours or so, and thereafter an olefin may be applied thereto andpolymerized in the presence of the thus-ripened catalyst. If desired,the catalyst components may be previously suspended in an inert solventor olefin, and then fed into the polymerization system.

In the invention, the post-treatment after polymerization may beeffected in any ordinary manner. For its details, referred to are thosementioned in the section of the first aspect of the invention.

According to the method of the invention, the powdery olefin polymerproduced has the advantages of high bulk density and narrow particlesize distribution. Other advantages of the invention are that thepolymer produced has good stereospecificity and that the catalyst usedhas high polymerization activity. For example, in homopolymerization ofpropylene in the method, produced is a propylene homopolymer having abulk density (kg/m³) of at least 345, preferably at least 380, andhaving good stereospecificity, and the catalyst used exhibits highpolymerization activity. In addition, the propylene homopolymer thusproduced has a particle size distribution index (P′) of smaller than4.0, P′<4.0, preferably smaller than 3.8, P′<3.8. That is, the particlesize distribution of the propylene homopolymer is narrower than that ofconventional propylene homopolymers. When compared with conventionalpropylene homopolymers of which the mean particle size is nearly thesame as that of the propylene homopolymer produced according to themethod of the invention, the propylene homopolymer produced in theinvention has a smaller degree of sphericity (S′) than that of theconventional propylene homopolymers. For its powdery morphology, theparticles of the propylene homopolymer produced in the invention arenearer to complete spheres than those of conventional propylenehomopolymers.

The invention is described in more detail with reference to thefollowing Examples, which, however, are not intended to restrict thescope of the invention.

The methods for analyzing and evaluating the polymers of the inventionare described below.

(1) Stereospecificity [mmmm]

For its details, referred to are those mentioned in the section of thefirst aspect of the invention.

(2) Particle Size Distribution Index (P) of Magnesium Compound

For its details, referred to are those mentioned in the section of thefirst aspect of the invention.

(3) Sphericity (S) of Magnesium Compound

For its details, referred to are those mentioned in the section of thefirst aspect of the invention.

(4) Particle Size Distribution Index (P′) of Polyolefin Powder

For its details, referred to are those mentioned in the section of thefirst aspect of the invention.

(5) Sphericity (S′) of Polyolefin Powder

For its details, referred to are those mentioned in the section of thefirst aspect of the invention.

(6) Bulk Density of Polyolefin Powder

Measured according to JIS K6721.

EXAMPLE II-1

(1) Preparation of Magnesium Compound

0.155 dm³ (2.64 gram atoms) of dewatered ethanol, 0.31 dm³ of n-heptane,0.8 g (6.3 milligram atoms) of iodine, and 8 g (0.33 gram atoms) ofmetal magnesium were put into a 0.5 dm³ three-neck flask equipped with astirrer and purged with nitrogen, and these were reacted with stirring(5.83 sec⁻¹, 350 rpm) at 40° C. until hydrogen gas was no moregenerated. Next, 0.124 dm³ of n-heptane was added thereto, and cooled toroom temperature. The solid thus formed was taken out and dried toobtain a magnesium compound.

(2) Preparation of Solid Catalyst Component

A 0.5 dm³ three-neck flask equipped with a stirrer was purged withnitrogen, and 16 g of the magnesium compound obtained in the step (1)was put thereinto, to which was added 0.080 dm³ of dewatered octane.This was heated at 40° C., and 0.0024 dm³ (23 mmols) of silicontetrachloride was added thereto and stirred for 20 minutes, to which wasadded 0.0035 dm³ (13 mmols) of di-n-butyl phthalate. The resultingsolution was further heated up to 80° C., and 0.062 dm³(0.56 mols) oftitanium tetrachloride was dropwise added thereto through a droppingfunnel. Next, the flask was still further heated to have an innertemperature of 125° C., at which the compounds therein were contactedwith each other for 2 hours. After this, the reaction mixture was fullywashed with dewatered octane. 0.107 dm³ (0.98 mols) of titaniumtetrachloride was added to this, and heated to have an inner temperatureof 125° C., at which the compounds were again contacted with each otherfor 2 hours. Next, this was fully washed with dewatered octane. Thus wasobtained a solid catalyst component.

(3) Propylene Slurry Polymerization

A one dm³ stainless autoclave equipped with a stirrer was fully driedand purged with nitrogen, and 0.4 dm³ of dewatered heptane was put intoit. 2.0 mmols of triethylaluminium and then 0.25 mmols ofdicyclopentyldimethoxysilane (DCPDMS) were added thereto in that order.Then, 0.0025 mmols, in terms of Ti, of the solid catalyst componentprepared in (2) was added thereto, and hydrogen (0.1 MPa) and propylenewere introduced thereinto in that order to have a total pressure of 0.8MPa. With that, the monomer propylene was polymerized at 80° C. for 1hour. Next, the system was cooled and degassed, and the reaction mixturewas taken out of it. This was put into 2 dm³ of methanol, and then driedin vacuum to obtain polypropylene. The results are given in Table II-1.

COMPARATIVE EXAMPLE II-1

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated, except that n-heptanewas not added to the system herein.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-1. The particle size distribution index (P) of thecarrier was over 4.0; and the bulk density of the polymer obtained was310 (kg/m³) and was low.

COMPARATIVE EXAMPLE II-2

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated, except that n-heptanewas not added, that the amount of iodine added was 0.24 g (1.9 milligramatoms) and that the number of revolution was 8.75 sec⁻¹ (525 rpm).

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-1. The particle size distribution index (P) of thecarrier was over 4.0; and the bulk density of the polymer obtained was310 (kg/m³) and was low.

EXAMPLE II-2

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated, except that 0.031 dm³of n-heptane was in the system during reaction and that 0.031 dm³ ofn-heptane was therein during solid precipitation.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-1.

EXAMPLE II-3

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated, except that 0.031 dm³of n-heptane was in the system only during reaction.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-1.

EXAMPLE II-3

(1) Preparation of Magnesium Compound

The same process as in Example II-3 was repeated, except that 8 mg(0.063 milligram atoms) of iodine was added to the system herein.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-1. The particle size distribution index (P) of thecarrier was over 4.0; and the bulk density of the polymer obtained was290 (kg/m³) and was low.

EXAMPLE II-4

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated, except that 0.031 dm³of n-heptane was in the system only during solid precipitation.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-2.

EXAMPLE II-5

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated, except that 0.155 dm³of n-heptane was in the system only during solid precipitation.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-2.

EXAMPLE II-6

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated, except that 0.155 dm³of n-decane was in the system only during solid precipitation.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-2.

EXAMPLE II-7

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated, except that MgCl₂ (0.3g, 6.3 milligram atoms per Cl) was used for the halide herein.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-2.

COMPARATIVE EXAMPLE II-4

(1) Preparation of Magnesium Compound

The same process as in Example II-7 was repeated, except that n-heptanewas not used herein.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated, except that themagnesium compound prepared as above was used herein.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except that the solidcatalyst component prepared as above was used herein. The results aregiven in Table II-2. The particle size distribution index (P) of thecarrier was over 4.0; and the bulk density of the polymer obtained was340 (kg/m³) and was low.

EXAMPLE II-8

(1) Preparation of Magnesium Compound

The same process as in Example II-1 was repeated.

(2) Preparation of Solid Catalyst Component

The same process as in Example II-1 was repeated.

(3) Propylene Slurry Polymerization

The same process as in Example II-1 was repeated, except thatcyclohexylisobutyldimethoxysilane (CHIBDMS) and notdicyclopentyldimethoxysilane (DCPDMS) was used herein for the silanecompound. The results are given in Table II-2.

Industrial Applicability

According to the invention, obtained are powdery olefin polymers havinggood stereospecificity, high bulk density and narrow particle sizedistribution, and the catalyst used exhibits high polymerizationactivity.

TABLE II-1 Example II-1 Comp. Ex. II-1 Example II-2 Comp. Ex. II-2Example II-3 Comp. Ex. II-3 Saturated Hydrocarbon heptane none noneheptane heptane heptane Amount of Hydrocarbon during reaction (dm³)0.031 0 0 0.031 0.031 0.031 Amount of Hydrocarbon after reaction (dm³)0.124 0 0 0.031 0 0 Amount of EtOH during reaction (dm³) 0.155 0.1550.155 0.155 0.155 0.155 Halogen or Halogen Compound iodine iodine iodineiodine iodine iodine Halogen or Halogen Compound/Mg (by gram atom) 0.0190.019 0.0057 0.019 0.019 0.00019 Number of Revolution (sec⁻¹) 5.83 5.838.75 5.83 5.83 5.83 Mean Particle Size of Carrier (μm) 41 70 43 42 44500 Sphericity of Carrier (S) 1.20 1.21 1.35 1.19 1.21 1.80 ParticleSize Distribution Index of Carrier (P) 3.8 4.3 4.8 3.7 3.8 7.2 SilaneCompound DCPDMS DCPDMS DCPDMS DCPDMS DCPDMS DCPDMS Stereospecificity(mol %) 98.4 98.2 98.0 98.4 98.2 98.0 Activity (kg/g-cat.) 11 14 13 1213 14 Mean Particle Size of Polymer (μm) 900 1800 1500 1000 1100 1200Sphericity of Polymer (S′) 1.21 1.20 1.32 1.20 1.22 1.75 Particle SizeDistribution Index of Polymer (P′) 3.7 4.2 4.6 3.6 3.7 7.0 Bulk Densityof Polymer (kg/m³) 450 310 310 440 430 290

TABLE II-2 Example II-4 Example II-5 Example II-6 Example II-7 Comp. Ex.II-4 Example II-8 Saturated Hydrocarbon heptane heptane decane heptanenone heptane Amount of Hydrocarbon during reaction (dm³) 0 0 0 0.031 00.031 Amount of Hydrocarbon after reaction (dm³) 0.031 0.155 0.155 0.1240 0.124 Amount of EtOH during reaction (dm³) 0.155 0.155 0.155 0.1550.155 0.155 Halogen or Halogen Compound iodine iodine iodine MgCl₂ MgCl₂iodine Halogen or Halogen Compound/Mg (by gram atom) 0.019 0.019 0.0190.019 0.019 0.019 Number of Revolution (sec⁻¹) 5.83 5.83 5.83 5.83 5.835.83 Mean Particle Size of Carrier (μm) 45 42 43 42 75 41 Sphericity ofCarrier (S) 1.20 1.21 1.20 1.21 1.23 1.20 Particle Size DistributionIndex of Carrier (P) 3.6 3.7 3.7 3.8 4.8 3.8 Silane Compound DCPDMSDCPDMS DCPDMS DCPDMS DCPDMS CHIBDMS Stereospecificity (mol %) 98.4 98.298.2 98.2 98.2 97.8 Activity (kg/g-cat.) 13 12 11 12 13 9 Mean ParticleSize of Polymer (μm) 1100 1000 900 1000 1700 900 Sphericity of Polymer(S′) 1.20 1.22 1.22 1.21 1.23 1.22 Particle Size Distribution Index ofPolymer (P′) 3.7 3.6 3.8 3.8 4.7 3.7 Bulk Density of Polymer (kg/m³) 420430 430 440 340 430

What is claimed is:
 1. A magnesium compound consisting essentially of amagnesium dialkoxide, prepared by reacting metallic magnesium, analcohol and 0.0001 to less than 0.06 gram atom, in terms of halogenatoms relative to one gram atom of magnesium, of a halogen and/or ahalogen-containing metal compound, at 30° to 60° C.
 2. The magnesiumcompound as claimed in claim 1, wherein the halogen is iodine.
 3. Themagnesium compound as claimed in claim 1, wherein the halogen-containingcompound is magnesium chloride.
 4. The magnesium compound as claimed inclaim 1, wherein the alcohol is ethanol.
 5. The magnesium compound asclaimed in claim 1, wherein the amount of alcohol ranges from 5 to 50mols relative to one mole of magnesium.
 6. The magnesium compound asclaimed in claim 1, wherein the ratio of halogen or a halogen compoundto magnesium, on a gram atom basis, is 0.019 or less.
 7. A solidmagnesium compound as claimed in claim 1, wherein the particle sizedistribution index (P) as defined in formula (I-1), is smaller than 4.0,P<4.0: P=(D ₉₀ /D ₁₉)  (I1) wherein D₉₀ indicates the particle diameterof the compound particles corresponding to the cumulative weightfraction of 90% in the particle size distribution thereof computed fromlight transmittance through a suspension of the compound particles in ahydrocarbon; and D₁₀ indicates the particle diameter of the compoundparticles corresponding to the cumulative weight fraction of 10%therein.
 8. The magnesium compound as claimed in claim 7, wherein themean particle size ranges from 38 to 60 μm.
 9. A magnesium compoundconsisting essentially of a magnesium dialkoxide prepared by reactingmetallic magnesium, an alcohol and at least 0.0005 to less than 0.06gram atoms, in terms of halogen atoms relative to one gram atom ofmagnesium, of a halogen and/or a halogen-containing metal compound, inthe presence of a saturated hydrocarbon compound.
 10. The magnesiumcompound as claimed in claim 9, wherein the halogen is iodine.
 11. Themagnesium compound as claimed in claim 9, wherein the halogen-containingcompound is magnesium chloride.
 12. The magnesium compound as claimed inclaim 9, wherein the alcohol is ethanol.
 13. The magnesium compound asclaimed in claim 9, wherein the ratio of halogen or a halogen compoundto magnesium, on a gram atom basis, is 0.019 or less.
 14. A solidmagnesium compound as claimed in claim 9, wherein the particle sizedistribution index (P), as defined in formula (I-1), is smaller than4.0, P<4.0: P=(D ₉ /D ₁₉)  (I-1) wherein D₉₀ indicates the particlediameter of the compound particles corresponding to the cumulativeweight fraction of 90% in the particle size distribution thereofcomputed from light transmittance through a suspension of the compoundparticles in a hydrocarbon; and D₃₀ indicates the particle diameter ofthe compound particles corresponding to the cumulative weight fractionof 10% therein, and whose particles have a sphericity (S), as defined informula (I-2), of smaller than 2.0, S<2.0: S=(L ₁ /L ₂)³ wherein L₁indicates the major diameter of the magnesium compound particle preparedby imaging the compound through scanning electronic microscopy followedby analyzing the projected image of the particle, and L₂ indicates thediameter of the circle having the same area as the projected area of themagnesium compound particle.
 15. The magnesium compound as claimed inclaim 14, wherein the mean particle size ranges from 38 to 60 μm.
 16. Amagnesium compound consisting essentially of magnesium dialkoxideprepared by reacting a combination of reactants consisting essentiallyof metallic magnesium, a hydrocarbyl alcohol and 0 0001 to less than0.06 gram atoms, in terms of halogen atoms relative to one gram atom ofmagnesium, of a halogen and/or a halogen-containing metal compound, at30° to 60° C.
 17. A magnesium compound consisting essentially ofmagnesium dialkoxide prepared by reacting a combination of reactantsconsisting essentially of metallic magnesium, a C₁₋₆-aliphatic alcoholand 0.0001 to less than 0.06 gram atoms, in terms of halogen atomsrelative to one gram atom of magnesium, of a halogen and/or ahalogen-containing metal compound, at 30° to 60° C.
 18. A magnesiumcompound consisting essentially of magnesium dialkoxide prepared byreacting metallic magnesium, a C₁₋₆-aliphatic alcohol and at least0.0005 to less than 0.06 gram atoms, in terms of halogen atoms relativeto one gram atom of magnesium, of a halogen and/or a halogen-containingmetal compound, in the presence of a saturated hydrocarbon compound. 19.A magnesium alkoxide compound consisting essentially of a magnesiumdialkoxide prepared by reacting metallic magnesium, an alcohol and0.0001 to less than 0.06 gram atom, in terms of halogen atoms relativeto one gram atom of magnesium, of a halogen and/or a halogen-containingmetal compound, at 30° to 60° C., the particulate magnesium dialkoxidecompound obtained having a mean particle size ranging from 38 to 60 μm,a degree of sphericity S of less than 2 and a particle size distributionindex (P) of less than 4.0.